The present disclosure relates to a fuel injection controller and a fuel injection control method for an internal combustion engine.
Japanese Laid-Open Patent Publication No. 2006-183537 discloses a fuel injection controller used for an internal combustion engine having an electromagnetic direct injector for injecting fuel into a cylinder. The fuel injection controller of the publication performs catalyst rapid warm-up control to warm up the exhaust purification catalyst when predetermined conditions are satisfied, such as a condition that the temperature of the internal combustion engine is low during startup. In addition, during the catalyst rapid warm-up control, the fuel injection controller of the publication controls the direct injector to perform single injection or split injection according to the operation state of the internal combustion engine. The single injection is an injection mode in which the amount of fuel required for each combustion is injected in one fuel injection. The split injection is an injection mode in which the amount of fuel required for each combustion is divided and injected in multiple fuel injections.
When the combustion state of the internal combustion engine deteriorates, such as when inferior fuel is supplied to the internal combustion engine, the engine speed decreases. To avoid excessive decrease in the engine speed, the fuel injection controller may perform the single injection, which is more effective at increasing the torque than the split injection. However, when the single injection is performed during the catalyst rapid warm-up control, the warm-up process of the catalyst slows down as compared to when the split injection is performed. As such, self-diagnosis of the warm-up state is desirable when the single injection is performed during the catalyst rapid warm-up control.